Device for applying adhesive to a workpiece

ABSTRACT

An adhesive robot, comprising a device for applying adhesive to a workpiece. The adhesive robot has a nozzle head ( 18 ), which has an application nozzle ( 24 ) and can be supplied with a pressurized viscous adhesive, the nozzle head ( 18 ) and the workpiece ( 14 ) being displaceable in relation to one another. The adhesive which is issued from the application nozzle ( 24 ) in a spray jet ( 28 ) is applied to a workpiece ( 14 ) along a predefined line of application ( 36 ) in the form of a strip of adhesive ( 40 ). To facilitate the adjustment and re-calibration process, the system comprises at least one camera unit ( 42 ), which is located on the nozzle head ( 18 ) and whose leans is directed towards the spray jet ( 28 ) or the adhesive strip ( 40 ). The output of said camera unit is connected to an image evaluation unit ( 45 ). The image data ( 40 ) recorded by the camera unit ( 42 ) is buffered and compared with predetermined image values ( 40 ). The decisive control parameters for the system can be calibrated and tracked either automatically or by remote control, on the basis of deviations in the image data that have been determined along the line of application ( 36 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 10/381,950, filed on Jun. 30, 2003, now U.S. Pat.No. ______, which is incorporated herein by reference in its entirety.No new matter is contained in this continuation application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a device for applying adhesive to a workpiece,the device including a nozzle head that can be supplied with viscousadhesive under pressure and an application nozzle, wherein the nozzlehead and the workpiece are moveable relative to each other via roboticmeans, such that the adhesive emitted from the application nozzle,preferably in the manner of a spray jet, is applied to the workpiece inthe form of an adhesive strip along a predefined line of application. Inthe following the term “adhesive” is intended to include other viscousmaterials, such as insulation, which can be applied to a workpiece inviscous form via an application nozzle.

2. Description of the Related Art

In the application of adhesives it is known to apply a viscous adhesive,with or without air manipulation, onto the workpiece in the form of anadhesive strip along an application line. It is further known to deflectand swirl a thread of adhesive emitted from an application nozzleaccording to the whirlwind principle with the aid of compressed gas andin this manner to apply upon the workpiece a strip-like, partially open,strip of material of defined breadth (EP 0576498 B1). With this type ofapplication it has also been taken into consideration, the recognitionthat depending upon the viscosity or stiffness of the adhesive material,a more or less viscous or tenacious adhesive thread is emitted, eventhough the flow amount of material out of the application nozzle of thenozzle head remains the same and that, one on the other hand, dependingupon the viscosity or tenacity of this thread, a greater or lesser gasstream is required in order to deflect the thread in predefined mannerand to produce a defined strip breadth. For this, a parameter whichdepends upon the viscosity of the pasty material is measured, and theamount of compressed gas supplied for the time interval is so controlledin functional dependence upon the measured viscosity parameter, suchthat a material strip of constant breadth is sprayed along theworkpiece. As viscosity dependent parameter one could consider theextrusion pressure of the material, the temperature of the pastymaterial and the drive pressure or, as the case may be, the drive outputof a dispensing or dosing device for the pasty material. In the casethat the compressed gas supply is made viscosity dependent, thisinvolves a control technical measure which requires a substantialcalibration effort. Above all in the case of the change of applicationparameters, in the case of changing the robot program or in the case ofchanging the adhesive or the workpiece surface, recalibrations arenecessary, which can be quite time consuming.

SUMMARY OF THE INVENTION

Beginning therewith it is the task of the invention to improve the knowndevices of the above-described type in such a manner that thecalibration process is automated during adhesive application and/or canbe carried out via remote control.

The solution of this task is proposed in accordance with the combinationof characteristics set forth in claims 1 and 6. Advantageous embodimentsand further developments of the invention can be seen from the dependentclaims.

The inventive solution is based upon the idea, that the adhesive stripcan be observed optically or can be scanned in the manner of a distanceprofile immediately after its application upon the workpiece, in orderin the case of unacceptable deviations from a reference image orreference profile to initiate a recalibration. In order to accomplishthis, it is proposed in accordance with the invention to provide atleast one camera unit, preferably a video camera or thermal (infrared)camera, on the nozzle head or on the associated robotic element, withits lens directed towards the spray beam or the adhesive strip, thecamera output connected to an image evaluation unit. In order tomaintain the illumination as constant as possible, it is advantageous toprovide a lighting or illumination unit on the nozzle head or on theassociated robotic element.

A further alternative or advantageous embodiment of the inventionenvisions the provision of a distance sensor on the nozzle head or on anassociated robotic element, directed towards the workpiece and scanningthe application line for determining the distance from the nozzle headto the workpiece or the thickness profile of the adhesive strip.

The camera unit can be for example a line camera of which the imagerecording cells are oriented perpendicularly or diagonally to theapplication line. Preferred as the camera unit is however a CCD-camerawhich produces in rapid sequence two dimensional frames which can bedigitally recorded and evaluated.

A preferred embodiment of the invention envisions that the imageevaluation unit includes an actual-value memory for continuous recordingof the measured image data as well as a path or clock time provider thatcan be synchronized with the actual-value memory along the line ofapplication. The image evaluation unit preferably includes a distance orlocation provider which is self-calibrating at predetermined calibrationpositions along the workpiece. These calibration positions or locationscould be either structural elements of the workpiece, such asinterruptions, edges or overlap locations, or a calibration mark orcalibration scale provided upon the workpiece especially for thisself-calibration.

According to a further preferred embodiment of the invention the imageevaluation unit includes an intended-value memory or generator forgeneration of predetermined image data along the application line. Theintended-value image data could be generated for example using a masterworkpiece (template) during a teaching run. Finally, the imageevaluation unit preferably includes a comparison circuit or routine forcomparing the actual and intended values of at least a portion of theimage data along the application line, of which the differential outputcould be a component of a control loop for the subsequent carrying outof the dispensing (application amount) and path parameters. For thispurpose the dispensing head can be supplied with adhesive via adispensing or dosing device, while the image evaluation unit and/or thedistance sensor component are a component of the dosing or dispensingdevice controlling control loop.

The dispensing device preferably includes a dispensed-amount controllerfor controlling the amount of adhesive as well as an actuator or controldevice for adjusting the strip-breadth of the adhesive along theapplication line. The dispensing controller could include a piston pumpwith a piston stroke or position sensor, of which the drive pressure ordrive force is variable with at least temporarily constantnozzle-opening cross-section. A preferred embodiment of the inventionenvisions that the nozzle head is a cyclonic spray head, of which theapplication nozzle is designed for emission of a coherent adhesivethread and which includes an air spray nozzle oriented diagonal to thedirection of emission of the adhesive thread. In addition, there isprovided a control device for adjusting the supply of spray airdepending upon the predetermined or intended strip breadth along theapplication line, which can however be influenced by a tracking orcompensating signal output of the image evaluation unit, extracted as adeviation or differential between the measured and the predeterminedstrip breadth. Alternatively, the nozzle head can be a cyclonic sprayhead, of which the application nozzle is designed for emission of acoherent adhesive thread and can be driven for rotation about aneccentric axis. Here also there is provided in addition a control devicefor adjusting the nozzle rotational speed according to the givendimensions of the strip breadth along the application line, which can beinfluenced by the tracking or compensating signal derived from an imageevaluation unit generated deviation or differential between the measuredand the predetermined strip breadth. In both alternatives the controlunit can be influenced on the input side using control parameters foradjusting the spray air supply or the nozzle rotation speed, which canbe derived from predetermined or measured adhesive amount per unit oftime or a viscosity dependent value or magnitude. The viscositydependent value can therein be proportional to the instantaneous drivepressure of a piston-pump type dosing or dispensing device.

A further preferred embodiment of the invention envisions that therobotic device includes an application line or path curve memory orgenerator for providing the path or the speed of the nozzle head alongthe application line.

Preferably the image evaluation unit is comprised of a control computerand image evaluation software. The image evaluation unit or the controlcomputer could preferably be networked with an external computer via anonline network. The external computer could on the other hand benetworked, preferably via the online network, with the control unit. Bythis means an online monitoring of the adhesive robot as well as theadaptation of the actuation and control parameters becomes possible froman external monitoring location such as, for example, using theinternet. The seamless and continuous image presentation makes possiblebesides this a rapid defect recognition and correction.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail onthe basis of the illustrative embodiment shown in the figures. There isshown:

FIG. 1 a robot for the flange or edge-bead sealing of a workpiece inperspective representation;

FIG. 2 a a section through a nozzle head connected to an end element ofthe robot;

FIG. 2 b an enlarged section according to FIG. 2 a in the area of theapplication nozzle;

FIG. 3 a schematic diagram of a control device for controlling thenozzle head for the robotic device according to FIG. 1;

FIG. 4 a schematic for explaining the intended/actual value comparisonin the control device according to FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The robot 10 shown in the figure is designed for application of adhesivefor sealing of edge beads or flange welds 12 of workpieces 14, hereparts for passenger vehicles. The robot carries for this purpose on itsend element 16 a nozzle head 18, which is supplied with a pasty adhesivevia a flexible hose 20 and includes an application nozzle 24 closeablevia a valve needle 22. The actuation of the valve needle 22 occurs via acylinder-piston arrangement 48, of which the piston 50, when in the openposition, is slid upward pneumatically by the robot control against theforce of a closing spring 51, and in the closed position is sliddownward under the influence of the closing spring 51. In the shownembodiment the nozzle head 18 is a cyclone spray head, wherein theadhesive thread 28 is emitted out of the application nozzle 24, whichthread is deflected and whirled with the aid of pressurized gas, suchthat a strip-like laid-down partially open adhesive strip 40 of definedbreadth is applied upon the workpiece 14. For this purpose the nozzlehead 18 includes a spray air connection 30, to which a spray airline isconnected. The spray air supplied thereby communicates with an airemission channel 34 oriented diagonal to the application nozzle 24.

The nozzle head is moveable via the robot 10 relative to the workpiece14 along a predetermined application line 36 in the direction of thearrow 38 and applies upon the workpiece 14 a whirled adhesive strip 40via the application nozzle 24.

As can be seen from FIGS. 1 and 3, on the end element 16 of the robot 10there is additionally provided a camera unit 42 with illumination device44, which is located aft of the nozzle head 18 in the direction ofmovement 38, and which has the task of monitoring the application of theadhesive strip 40 and, as necessary, to correct it using imageevaluation unit 45 actuation or control technology.

In addition to the camera unit 42 a distance sensor 46 is coupled withthe nozzle head 18, with which the distance of the application nozzle 24to the workpiece 14 is detected as an important adjustment parameter,and the thickness profile and/or the breadth of the adhesive strip 40can be determined. The distance sensor 46 carries out therein, in themanner of a scanner, a pendulum movement running transverse to theapplication track. The distance sensor 46 is, for example, a lasersensor or an ultrasound sensor.

The measurement data from the camera unit 42 and the distance sensor 46are input into an image data memory 47 for the determination of theactual data 40, and compared in a computer 49 at least partially via acomparison routine with predetermined intended data 40′. There can bemeasured, for example, the distance to the flange weld bead edge 12,12′, and the breadth and the thickness of the adhesive strip 40. Thecomparison data can thereby be converted to control parameters for thecontrol of the dispenser 52 or the spray air supply 54. The controlparameters take into consideration the speed of advance of the nozzlehead 18, the drive pressure of the dispenser 52, the spray air pressurein the spray air supply 54 or the distance of the application nozzle 24from the workpiece 14. Due to the high application speed a very rapidcamera 42 is necessary. Likewise desirable is a good and constantillumination via the illumination unit 44. Preferably each individualcamera image is illuminated using a flash bulb or an illumination unit44 in the form of a diode flash. The path measurement or navigationalong the application track 36 occurs preferably via a path provider ora path scale 57, which can be adjusted or interpolated using referencepoints fixed on the workpiece, such as reference boreholes, kinks,breaks or interruptions. In this way even the predetermined applicationpath 36 can be appropriately corrected as necessary via the robotcontrol according to the measured values.

The monitoring of the adhesive strip with the rapid video camera 42 andthe distance sensor 46 simplifies both the adjustability of the robot 10and the dispensing system 52, 54 as well as their resetting followingdisruptions, such as changing of material, temperature oscillations orintervention in the original set parameters. It is of particularadvantage herein that the setting and correction processes can becarried out also using external computers 56, for example from a servicestation, with use of an online network 58, such as the internet.

In summary the following can be concluded: The invention relates to anadhesive robot, comprising a device for applying adhesive to aworkpiece. The adhesive robot has a nozzle head 18, which has anapplication nozzle 24 and can be supplied with a pressurized viscousadhesive, the nozzle head 18 and the workpiece 14 being displaceable inrelation to one another. The adhesive, which is issued from theapplication nozzle 24 in a spray jet 28, is applied to a workpiece 14along a predefined line of application 36 in the form of a strip ofadhesive 40. To facilitate the adjustment and re-calibration process,the system comprises at least one camera unit 42, which is located onthe nozzle head 18 and whose lens is directed towards the spray jet 28or the adhesive strip 40. The output of said camera unit is connected toan image evaluation unit 45. The image data 40 recorded by the cameraunit 42 is buffered and compared with predetermined image values 40. Thedecisive control parameters for the system can be calibrated and trackedeither automatically or by remote control, on the basis of deviations inthe image data that have been determined along the line of application36.

1. A device for applying adhesive to a workpiece, comprising a nozzlehead (18), which has an application nozzle (24) and can be supplied witha pressurized viscous adhesive, wherein the nozzle head (18) and theworkpiece (14) are displaceable in relation to one another via roboticmeans (10) such that the adhesive, which is issued from the applicationnozzle (24), preferably as a spray jet (28), is applied to a workpiece(14) along a predefined line of application (36) in the form of a stripof adhesive (40), and wherein at least one camera unit (42), which islocated on the nozzle head (18) or an associated robotic element, withlens directed towards the spray jet (28) or the adhesive strip (40), ofwhich the output of said camera unit is connected to an image evaluationunit (45), wherein the image evaluation unit (45) includes an actualvalue memory (47) for continuous storage of the measured image data (40)as well as an impulse clock or a provider of position (57) along theapplication line (36) synchronizable with the actual value memory, andwherein the image evaluation unit (47) includes a clock or positionprovider self-calibrating at predetermined calibration locations alongthe workpiece (14).
 2. A device according to claim 1, wherein the imageevaluation unit includes an intended value memory or generator forgenerating predetermined image data (40′) along the application line(36).
 3. A device according to claim 2, wherein it is adapted togenerate the intended value image data (40′) in a teaching run.
 4. Adevice according to claim 1, wherein the image evaluation unit (45)includes a comparison circuit or routine for comparing theactual/intended values of at least a portion of the image data (40, 40′)along the application line (36).
 5. A device according to claim 1,wherein the nozzle head (18) is supplied with adhesive via a dispensingdevice (52), and that the image evaluation unit (45) and/or the distancesensor (46) are components of the control loop driving the dispensingdevice (52, 54).
 6. A device according to claim 5, wherein thedispensing device includes a volume control for adjusting the adhesivematerial flow as well as an actuation or control device (54) foradjusting the strip breadth of the adhesive along the application line(36).
 7. A device according to claim 6, wherein the robot (10) includesa navigator or a path curve memory or generator for adjusting the pathand the speed of the nozzle head (18) along the predeterminedapplication line (36).
 8. A device according to claim 6 wherein the flowcontroller includes a piston pump with a piston stroke measuring device,of which the drive pressure or force is variable in the case of an atleast temporarily constant application-nozzle opening cross-section. 9.A device according to claim 1, wherein the nozzle head (18) is suppliedwith adhesive via a pressure control (52) and that the image evaluationunit (45) and/or the distance sensor (46) are components of the controlloop driving the pressure control (52, 54).
 10. A device according toclaim 1, wherein the nozzle head (18) is a cyclone spray head, of whichthe application nozzle is adapted for output of a coherent adhesivethread (28), and which includes at least one spray air channel (34)oriented diagonal to the application nozzle (24), and that a controlunit (54) is provided for setting the spray air supply according to thevalue of the predetermined strip breadth along the application line(36), which can be acted upon by a tracking or adjusting signal derivedfrom the image evaluation unit (45), determined by the deviation of themeasured image data from the predetermined strip breadth.